There is a first conventional saddle-stitch and fold machine. As shown in FIG. 4 of Patent Document 1, the first conventional machine includes a saddle-stitcher that saddle-stitches sheets printed by a printer, and a folder that folds a sheet stack fed from the saddle-sticher. The sheet stack folded by the folder becomes one booklet.
As shown in FIG. 9A, the first conventional machine manufactures the booklet from a plurality of the sheets. The sheets are printed by the printer using a toner colorant. The toner colorant along a fold line may fall off an outer sheet (cover) 101a disposed on an outermost portion of the booklet 100, which is called as “toner crack 110”. Further, as shown in FIG. 9B, the first conventional machine cannot fold the sheet stack neatly because the fold line of the booklet is swelled, which is called as “swell”.
There is a second conventional saddle-stitch and fold machine. As shown in FIGS. 1 to 3 of Patent Document 1, the second conventional machine includes a creaser that forms a crease on all of the sheets printed by the printer; a saddle-stitcher that stacks the sheets fed from the creaser and saddle-stitches the sheet stack along the crease; and a folder that folds the sheet stack fed from the saddle-stitcher along the crease.
As described above, according to the second conventional machine, the creaser forms the crease on all of the sheets. Thus, the “toner crack 110” is not occurred on the “outer sheet (cover) 101a” even though the sheets are printed by the printer using a toner colorant. Further, the second conventional machine can fold the sheet stack neatly because the “swell” is not occurred along the fold line of the booklet.
However, according to the second conventional machine, the “toner crack 110” may be occurred on an “inner sheet 101b” that is disposed on an innermost portion of the booklet 100.
Patent Document 1: JP 2003-211865 A